All combat combines both defense and offense. However the traditional battlefield has almost always had a safe rear area to provide for the fighting forces. Current weaponry and support vehicles have been designed following this age old pattern: The fighting equipment and men defend the support equipment and men. Armored vehicle technology has been exclusively the domain of the Armored Fighting Vehicle. Armored fighting vehicles (AFVs), both tanks and armored personnel carriers (APCs), first saw limited use in World War I. These early AFVs were little more than crude armor boxes built on caterpillar-tracked tractors. Both armor and weaponry have escalated dramatically since then.
In the early 1930s, shaped-charged warheads were developed that offered vastly superior armor penetrating performance coupled with ease of use and employment. The basic principle of the shaped-charge warhead is a concave or cone shaped hollow area in one end of the explosive core of the warhead. This hollow area is lined with a metal, typically copper. Upon detonation, the metal liner is compressed into a jet of very dense, superplastic metal moving at a speed of approximately 30,000 feet per second. While the actual material properties and physical behaviors are still not very well understood, the hypervelocity jet of metal can punch a hole in steel plate armor many times thicker than the diameter of the shaped-charge warhead.
Detonation distance is critical because the jet disintegrates and disperses after a relatively short distance (no more than 2 meters typically). The critical factor to the effectiveness of a shaped-charge, or high explosive anti-tank (HEAT), round is the diameter of the warhead. As the jet penetrates the armor, the width of the hole decreases leading to a characteristic “fist to finger” penetration effect. That is, the size of the eventual “finger” penetrating into the AFV depends on the size of the original “fist”. In general, a HEAT round will penetrate armor thickness 150% to 250% of their diameter, although modern versions, such as the latest Russian RPG-7V, claim penetration ratios as high as 700% of the warhead diameter.
By the end of World War II, various anti-tank weapons had been developed and deployed that could be carried by one man to defeat AFVs, including hand-thrown grenades (e.g. Russian RPG-43) and warheads mounted on a rocket and launched from a rocket launcher (e.g. United States M7A1-“Bazooka”). Since World War II, HEAT rounds have become almost universal as the primary anti-vehicle weapon, because it can be used against all AFV and unarmored targets such as trucks and other general purpose vehicles or bunkers.
In modern warfare, man-portable anti-tank weapons represent one of the greatest threats on the battlefield. These weapons are relatively light, easy to transport, and can defeat most AFV armor if the AFV is struck in a vulnerable location. The Soviet RPG-7 is the probably the most ubiquitous of these weapons, because it has been produced by most Soviet client states including all of the former Warsaw Pact countries, Egypt, Libya, Iraq, Iran, China, North Korea, and numerous other countries, and it has been widely disseminated by these numerous producing countries. The RPG-7's maximum effective range against moving targets is 300 meters and the maximum range is 920 meters, and it can penetrate up to 600 millimeters (23 inches) of rolled homogeneous steel armor.
In the technology race of anti-tank weaponry versus armor protection, AFV armor protection technology has attempted to match increased lethality. Armor protection has improved dramatically and increasing use has been made of more unconventional means to increase protection. One of the unconventional modifications used in unconventional combat has been the use of standoff screens around a fighting vehicle to prevent shaped charges from detonating against the vehicle armor. Sand bags have also served as additional armor as have water cans.
While many armor advances have been proven effective and have been deployed on heavy AFVs, there has been virtually no effort to protect lighter non-combat vehicles such as trucks and the M998 HMMWV family of vehicles. While the M998 series has been modified with additional armor to increase protection against large caliber bullets and land mines, there has been little progress at protecting these rear echelon support vehicles from light anti-tank HEAT warheads, since it was believed that they were going to be protected by the fighting vehicles in the historic battlefield configuration
The current situation faced by United States military forces in Iraq and Afghanistan has underscored the reality that rear echelon, support forces and their attendant vehicles are more likely, because of this vulnerability, to come under fire from light anti-tank weapons. Various irregular combatants are increasingly attacking support and rear echelon areas and bringing light vehicles under fire with RPGs and improvised munitions, such as artillery shells rigged as command-detonated mines. There is a need for a robust, light armor system that can be retrofitted on existing vehicles or be incorporated into new designs to provide effective HEAT warhead protection without a prohibitive weight penalty.